1. Field of the Invention
The present invention relates to a method of folding an air bag body.
2. Description of the Related Art
Conventionally, there has been known, for example, an air bag apparatus provided in a steering wheel of a motor vehicle. The air bag apparatus is provided with an air bag body formed in a flat bag shape, a cover covering the air bag body, an inflator injecting gas, and the like. Then, the air bag body is folded to be small in accordance with a certain method at unactivated state so as to be received inside the cover. At a time of detecting an impact of collision by a collision sensor, the air bag body is expanded by injecting the gas from the inflator. The cover is broken due to an expansion pressure of the air bag body and the air bag body is protruded, expanded and deployed to face the passenger, so that the impact of the collision to a passenger is reduced.
The air bag body has been conventionally folded along a straight line at a predetermined position from a state being expanded on a flat plate so as to be formed in a rectangular parallelepiped shape capable of being received in the cover. However, there is a problem that it is hard to mechanically produce the folded air bag body, a lot of labor is required and it is hard to improve the productivity.
In order to improve the above mentioned points, as a folding method suitable for the automation, for example, there has been known a structure shown in International Patent Publication Laid-Open No. WO97/48580. In particular, the air bag body is expanded by using a folding apparatus provided with a folding plate arranged so as to form a coaxial circle shape or a spiral shape in opposite to each other from upper and lower portions of the air bag body. The air bag body is folded by gripping the air bag body by the folding plates, moving or deforming the folding plates toward predetermined hollow space so as to reduce distance between each of adjacent folding plates. However, in this structure, there is a problem that the structure of the apparatus becomes complex and it is not easy to reduce the production cost.
Further, with respect to, for example, the air bag body formed in a flat circular shape, there has been proposed a so-called petal fold in which the air bag body is collected toward a center from an outer peripheral portion thereof so as to form a pleat shape. With respect to this method, there have been known structures described in Japanese Patent Publication Laid-Open Nos. 10-129381, 10-217894 and the like.
At present, there is required a structure of an air bag body which can improve the deploying characteristic and reduce the production cost.
The present invention is made by taking the points mentioned above into consideration, and an object of the present invention is to provide a method of folding the air bag body in which the deploying characteristic is improved and the production cost can be reduced.
The first aspect of the invention provides a method of folding an air bag body having a first surface portion with an inlet port through which gas is introduced into the air bag body and a second surface portion opposing to the first surface portion, the method comprising the steps of: restricting the first surface portion and the second surface portion to be close to each other along a plurality of lines toward the inlet port; expanding the air bag body so that at least a part of one surface portion of the first and second surface portions other than the portion which is restricted, whereby putting the part of the first surface portion and the second surface portion away from the other; accumulating a portion between the portions restricted along the lines toward the inlet port; and pressing the portion restricted along the line against an outer periphery of the accumulated portion.
According to the first aspect of the invention, the air bag body is restricted in the state that the first surface portion and the second surface portion are close to each other along the line toward the inlet port. The other portions than the restricted portion are expanded without being restricted, whereby the first surface portion and the second surface portion are moved apart from each other. In this state, the first surface portion and the second surface portion are respectively folded in a wave shape without being engaged with each other by pressing and accumulating the portion between the lines, that is, the first surface portion ant the second surface portion toward the inlet port. Further, the portion restricted in the state of being close to each other is pressed against the outer periphery of the accumulated portion. In the air bag body folded in the manner mentioned above, the gas introduced from the inlet port is smoothly supplied to the peripheral edge portion, and it is easy to improve the deploying characteristic. Further, in the air bag body, a height in a front surface of the air bag body is not restricted at a time of accumulating. Accordingly, a large member needed at a time of restricting the height of the front surface is not required, and it is possible to rapidly perform the folding operation by the apparatus having a simple structure, and the production cost can be reduced.
The second aspect of the invention provides a method of folding an air bag body having a first surface portion with an inlet port through which gas is introduced into the air bag body and a second surface portion opposing to the first surface portion, the method comprising the steps of: expanding the air bag body, whereby putting the first surface portion and the second surface portion away from each other; restricting the first surface portion and the second surface portion to be close to each other along a plurality of lines toward the inlet port; accumulating a portion between the portions restricted along the lines toward the inlet port; and pressing the portion restricted along the line against an outer periphery of the accumulated portion.
The third aspect of the invention provides a method of folding an air bag body according to aforementioned aspects of the invention, further comprising the steps of; displacing the second surface portion facing the inlet port toward the first surface portion; and gathering the second surface portion facing the inlet port toward the first surface portion to form a forefront deploying portion, wherein restricting force applied to the air bag body is reduced before the pressing step is completed, wherein the air bag body is formed as an asterisk shape after the accumulating step is completed, and wherein the air bag body comprising the first and second surface portions formed as circular shape and the inlet port located at a central portion of the first surface portion.